Tangent bender and expansible die combination



u y 5 c. J. BATH TANGENT BENDER AND EXPANSIBLE DIE COMBINATION 2 Sheets-Sheet 1 Filed Aug. 11, 1949 y 18, 1950 c. J. BATH TANGENT BENDER AND EXPANSIBLE DIE COMBINATION Filed Aug. 11, 1949 2 Sheets-Sheet 2 R m W W.

Patented July 18, 1950 UNITED STATES PATENT OFFICE.-

TANGENT BENDER AND EXPANSIBLE DIE COMBINATION Claims.

stock to be formed. In general such machines I are employed to bend large flat sheets of stock, having upturned flanges along their lateral margins, normal to the general plane of the sheet so that the marginal flanges extend inwardly of the formed piece. This is accomplished by engaging the flat sheet of stock, after its marginal flanges have been formed, between male and female die members, the female die generally being stationary and engaging the outer face of thesheet of stock and the male die being movable into and out of engagement with the opposite or inner face of the sheet between the flanges. After engagement of the sheet between the male and female die members in this manner, wing dies are operated to bend the sheet and lay its end portions against lateral faces of the male die. The female die has a working face which is channeled so that it engages not only the outer face of the flanged stock but also the outer surfaces of the flanges. The wing dies are similarly channeled so that while engaging the flat outer face portions of the stock at opposite sides of the male die, they also engage the outer surfaces of the flanges. The flanged sheets are held to proper dimensions between the outer surfaces of the marginal. flanges so that the female die and the wing dies may snugly engage the outer surfaces of the flanges as well as the outwardly exposed face of the stock. However, many structures require a marginal flange at one margin of the sheet which is relatively thick. For example, such is generally required in the case of refrigerator cabinets and the like. In such instances the metal of the margin of the sheet is folded upon itself one or more times so that the flange is from two to three thicknesses of the metal stock. Qbviously a variation of a few thousandths in the thickness of the stock results in a substantial change in the dimension between the inner faces of the flanges and it is necessary that the male die accommodate itself to the resulting variation 2 havebeen used heretofore to compensate for the varying dimension of the sheet between these inner surfaces of the marginal flanges. The expansi-ble dies of the prior art have been operated by operating pins which protrude through the operating face of the male die and are operated to expand the die by the pressure applied to the pins, through the medium of the metal between the dies, by the female die as the dies are closed. Such an arrangement has a disadvantage that the expansion always occurs at the same point and always is the same in amount. Since there is considerable variation in metal thick ness of the stock, the expansion of such a die results in inadequately filling the space between the flanges in many instances, and in overfilling and consequently binding too tightly against the metal in other instances. Furthermore the male die necessarily continues to remain in contact with the inner surfaces of the flanges while the wing dies are being released and retracted to open position, this release and return of the wing dies occurring while the male and female dies are closed. This is undesirable in that the metal of the marginal flanges is compressed too tightly between the male die and the wing dies and accordingly tends to be torn off of the male die or marred by the wing dies as they are moved to open position.

Again, since the expanding movement of the male die is in fixed relation to the degree of closure of the male and female dies, the pressure applied by it increases in direct proportion to the thickness of stock. Thus little latitude in the cycling of the tangent bender to meet the wide variations in stock thickness is permitted.

The present improvement resides principally in the combination with the Wing dies of a male die which is expansible independently as to time, amount, and pressure, relative to the closure of the male and female dies so that it can be expanded the proper amount and at the proper pressure to compensate for the variations in dimensions between the marginal flanges of the stock resulting from variations in the stock thickness and thus snugly engage the inner surfaces of the flanges at desired predetermined pressure preparatory to and during closure of the wing dies and then released prior to opening of the wing dies so that the flanges of the stock can spring back slightly and the Wing dies then can free themselves" readily from the formed piece and be returned to open position without scufiln-g the piece or tearing it off of the male die.

Furthermore, the improvement makes possible sheet properly and form it properly therebetween after which the male die may be expanded, the

wing dies closed, the expanding pressure released,

the wing dies then withdrawn, and the male and female dies opened.

For the purposes of illustration the present invention is described as applied in the formation from a flat sheet of metal stock of a cabinet, such as the conventional domestic refrigerator cabinet, which, along one face, has a, marginal peripheral flange of one thickness of metal and along the other face has a marginal peripheral flange of three thicknesses of metal, its use in the formation of parts of other articles being apparent from the illustrative example.

I8 which is operable by fluid or hydraulic pressure to swing the frame about its pivotal axis for causing the plates I4 of the wing dies to roll from the open position illustrated in Fig. 1 around the rounded lateral margins of the male die and lay the sheet of stock to be formed against the lateral faces of the male die.

As mentioned; the piece of sheet stock to be formed is one having marginal flanges at its upper and lower margins and accordingly the working face of each plate I4 is channel-shaped and has upper and lower marginal portions I9 which The objects and advantages of the present invention will become apparent from the follow ing description wherein reference is made to the drawings in which:

Fig. l is a top plan view of a tangent bender embodying the principles of the present invention;

Fig. 2 is a side elevation of the tangent bender illustrated in Fig. 1;

Fig. 3 is an enlarged fragmentary side elevation of a portion of the tangent bender showing the male die and expanding mechanism therefor;

Fig. 4 is a front elevation of the male die member and expanding mechanism viewed from the right in Fig. 3 and,

Fig. 5 is a fragmentary view of the male die member and sectional view of the forming plate of one of the wing dies showing the cooperative relation thereof when forming the stock. I

Referring to the drawings, the illustrative embodiment of the tangent bender is one in which the forming faces of the male and female dies are upright. The bender comprises essentiallya frame I- on which is mounted a stationary female die 2 and a reciprocable male die 3. The male die is mounted on a suitable movable die carriage 4 which carries fluid pressure operated knockout mechanism 5 for freeing the formed work piece from the male die. The die carriage 4 is reciprocated by suitable power means such A pair of as a linkage 6 driven from a crank I. wing dies, indicated generally at 8, are carried by the frame I. As more fully described in the above identified patent, each of thewing dies comprises a rigid upright frame 9. which is pivotally connected by upright pivots ID to suitable supports II which are fixedly mounted on the frame I of the machine. A spring pressed roller I2 is mounted in the frame 9 for rotation about an axis parallel to the pivotal axes of the frame v .and for movement transversely of its axes. Adjustable compression springs I3 are carried by the frame 9 and are arranged to urge the roller provided at its upper and lower edges, beyond its.

working face, with racks I 6 which cooperate with stationary gear segments II securely fastened on the supports II.

Each frame 9 is arranged to be swung about its pivotal axis by suitable power means.

a double acting piston and cylinder assemblage The roller engaged surface or section 2 I.

are arranged to snugly engage the outer surfaces of the marginal flanges of the sheet stock.

The male die 3, when collapsed is arranged to lie between the marginal flanges of the sheet of stock of maximum thickness with slight operating clearance. However, since the dimension between the flanges varies considerably as explained, it is necessary that the male die be expansible and contractible for the purpose of snugly engaging the inner surfaces of the marginal flanges regardless of the stock thickness and so remain during the bending of the sheet around the male die by the wing dies or plates I4, after closure of the male and female dies. As best illustrated in Figs. 3 and 4, the male die comprises a main upper section 20 which is detachably connected in fixed position to the carriage 4 and a lower movable section 2| which is movable vertically relative to the upper section 20 and to the carriage 4. The lower section 2I is supported for vertical movement by means of a supporting plate 22 which is secured by bolts 23 to the upper section 20 and is urged against the underside of the section 2! and upwardly toward the section 20 by means of suitable springs 24. The springs 24 are of adequate strength to hold the lower section 2| with its upper surface in firm juxtaposition with the under surface of the section 20 under normal operating conditions.

. Interposed between the sections 20'and 2I in a cavity in the section 2 I, is a wedge 25 which has a sloping wedge face on its under surface cooperable with a corresponding sloping surface on the upvwardly exposed bottom wall of the cavity in the Movement of the wedge 25 to the right in Fig. 3 lowers the section 2 I, thus expanding the male die 3 vertically against the force of the springs 24. Movement of the wedge .25 to the left in Fig. 3 releases the expanding pressure, so that the die is contracted by the springs 24. The

wedge 25 is provided with suitable slots to clear the bolts 23 during operation.

The wedge is provided with cam surfaces 21 engaged by a plurality of cooperating cams 28. The cams 23 are mounted on suitable slide rods 29, respectively, which extend vertically through the male die 3 and at their upper ends are connected to a rigid bracket 30. The bracket 30, in turn, is connected to pistons 3I which are operable in cylinders 32, of double acting piston and cylinder assemblages, the cylinders being fixedly mounted on a suitable bracket 33 secured in fixed position on the carriage 4. The cylinders 32 are connected at their upper ends to a pipe line 34 and at their lower ends to a pipe line 35. The pipe lines 34 and 35 are connected to a suitable four-way valve 36 which in turn is connected In the; illustrative example the power means comprises by a pressure .or inlet line 31 to a source of fluid pressure and by a return or exhaust line 38 to a suitable sump.

The valve 36 is operable selectively to admit rfluidto the upper end of the cylinders 32 through the line 34 and connect the lower end of the cylinders to a sump through the line 35 in one position of the valve'so as to move the pistons on their downward expanding stroke by fluid pressure and to reverse the connection. in another position of the valve for moving the pistons on their upward contracting stroke to starting po- 1 sition. The valve 36 may be operated manually but it is preferable to use a solenoid operated valve which, when energized, moves to said one position to expand the die and when deenergized is spring returned to its other position to contract the die, Though the valve may be operated by a manual switch itis preferred to operate it by switches 39 and 4G.

The switch 33 is a normally open self-restoring switch and is adiustably connected to the. frame l for movement. longitudinally thereof. so as to-be engaged and closed by the carriage 4 or by a. suitable abutment thereon at a preselected position of the carriage. It is operative when closed to energizethe solenoid to admit pressure fluid from the valve 36 to the upper end of the cylinder. It is preferably located such that air or fluid pressure is admitted to the cylinders 32 upon substantially complete closure of the male: and female dies. The switch 40. is a normally closed switch having a delayed. reclosure when released after being moved into open position. It is connected in series with the solenoid valve 36 and the switch 39. Itis adjustably mounted on the frame I in a position such that when the wing dies reach fully closed position they, or a suitable abutment thereon, engage the switch M1 and open it to-break the circuit tothe valve thus causing the valve 36 to return to its starting position and reverse the pressure fluid tothe. cylinders 32 and retract the cam- 25 so that the male die. contracts. Accordingly, the delayed return of the switch 40 to closed position after its release by the wing, dies is. such that. ample time is afforded to the male die to move. to open position, thus releasing the switch 39 and permitting it to move to open position before the switch 40 recloses itself. Thus the male die remains expandedduring closure of the wing dies and remains contracted during opening of the wing dies,

For example as illustrated in Fig. 3, the stock S, having upper flanges A and a lower flange B, shown as gripped between. the male and fi'emale dies with the flange A resting on the upper margin of. the male die. and the flange B dispose-d beneath the section 2| of the male die.- Upon admission of pressure fluid to the cylinders 32 when the male and female dies are thus closed, the section 2| is pressed with predetermined pressure, depending upon the pressure of the source ofair or fluid to the cylinders 32, against the inner face of. the lower flange B. Since the female die has a channel-shaped face so that the outer surfaces of the flanges A and B are both engaged and buttressed by the portions [9 of the female die, the lower section 2| can be moved only the amount per mitted' by the female. die and the interposed flanges A and B, Accordingly there is no danger of the flanges A and B being stressed and bent outwardly from their normal planes.

In operation of the apparatus the sheet is disposed in proper position between the male and female dies with the flanges A and B related to the male die as illustrated and the male die in contracted condition. The machine is then operated to close the male and female dies and upon closure thereof the male die is expanded,

6. asv described either by manual operation of the valve 36 or by virtue of the switch 39.

With the male and female dies held closed position manual controls are operated to cause the piston and cylinder assemblages [8 to rock the plates 14 of the wing dies about the upright lateral margins of the male die thus laying the metal stock S around the curved lateral margins of the male die and disposing the remainder of the stock at the desired angle to that portion of the stock gripped between the male and female dies. When the wing dies are moved inwardly to fully closed position they open the switch 40 thus causing the solenoid valve to reverse the connection to the cylinders 32 and thereby cause the pistons to contract the male die. After contraction of the male die the manual controls of the assemblages l8 are again operated to cause the assemblages to return the plates M to starting position, thus opening the wing dies. Since the switch 40 has a delayed closure the male die remains contracted during this operation. After opening of the wing dies the male die is retracted. The delayedreclosure of the switch 40 is such that the male die" can be retracted so as to permit self-opening of the switch 39 before the switch 40 recloses. Thus the apparatus is reset for a repetition of the cycle. Upon retraction of the male die from the female die the work piece remains supported thereon, having. been released by the plates Id of the wing dies. When the male die reaches fully retracted position. the work piece is. removed.

As' a result of the cycling thus made possible and due to the inherent. slight spring-back of the flanges A. and B, the flanges release from the wing dies as soon. as the male die contracts and the tendency of the wing dies to stick to and frictionally engage the outer surfaces of the flanges of the stock with a resultant tearing of the formed piece off of the male. die is eliminated. Were the expansion of the male. die continued during opening of the wing dies, there would be no spring-back in the flanges to permit the wing dies to free themselves from the flanges and consequently they would tend to tear the formed piece off of the male. die andscuff the surfaces of the flanges.

Again, since the expanding pressure and move ment of the section 2lof the male die 3 can be controlled independently of the closure of the male and female dies the same pressure can be maintained on the flanges by the male die regardlessof the thickness of the stock. On the other hand. were the expanding mechanism operated mechanically by movement of the: male dive into the female die, the amount. of expansive movement. of the male die would be fl-xed and therefore in. event the stock. were. excessively thick undue pressure would be exerted which might jam or damage the dies. or ruinthe piece, and if the stock were exceptionally thin. or undergauge, insufficient expansive movement. of the male: die would be permitted to assure engage-- merit of the maledie with the inner flange surfaces of the work piece and consequently the flanges would tend to become wrinkled or be improperly bent.

For clearness of description and of claiming the invention, the machine is described and claimed by reference to the specific vertical, horizontal and lateral directions of movement, it being apparent that these specific directions are not to be considered limitations, merely descriptions of relative positions and movements of the elements as obviously the position in which the machine operates is immaterial.

Having thus described my invention, I claim:

1.'In a tangent bender, a stationary female die, a cooperating reciprocable male die, a wing die cooperable with the male die to bend a sheet of metal which is gripped between the male and female 1dies against a lateral face of the male die, said male die having sections movable relative to each other in a direction transversely of the paths of both the male die and the wing die, fluid pressure operated means to expand the male die, means to contract the male die, and means for causing the fluid pressure operated means to expand the male die after closure of the male and female dies and prior to closure of the wing die, and to contract the male die while the male and female dies are closed and prior to opening of the wing die.

2. In a tangent bending machine including a female die, a wing die and a reciprocable male die cooperable with both the female die and wing die, a reciprocable carriage for the male die, a fluid pressure operated piston and cylinder as-- semblage mounted on said carriage, said male die having a section with a portion of the working face thereon and fixed relative to the carriage, and another section with a portion of the working face thereon and movable relative to the carriage for expansion and contraction of the male ,die, means operatively connectin the assemblage to the movable section of the male die for moving said section to expanded position by the assemblage, means to return the movable section to a starting position in which the male die is contracted, and valve means to control the operation of the assemblage for expanding the male die prior to closure of the wing die and for contracting the male die prior to opening the wing die.

3. In a tangent bending machine, a pair of main dies movable horizontally relatively toward and away from each other and having cooperating main working faces adapted to engage opposite faces of a portion of a sheet of material having spaced marginal flanges on one face, one of said dies having a lateral working face adapted to engage the flanged face of said portion of the sheet and having, at the top and bottom of, respectively, angularly disposed to, the lateral marginal faces adapted to engage the inner faces of the flanges of the sheet, a wing die mounted on the machine and having a main working face with top and bottom marginal faces, respectively, angularly disposed to the main face and adapted when the sheet is engaged between the main dies, to engage, beyond the portion of the sheet engaged by the main dies another portion of the sheet at the face opposite from the flanges and the outer faces of the flanges, and to bend said other portion so as to place its flanged face into juxtaposition with the lateral face of said one die and the inner faces of its flanges into juxtaposition with the said marginal faces of said one die, power means to open and close the main dies, power meansto open and close the Wing dies'while the main dies'areclosed, said one die being expansible and contractible vertically for causing said marginal faces'thereof toen-- gage the inner faces of the flanges, power means operable to expand and contract said one main die, and control means operable, selectively, to render the last mentioned power means while the main dies are closed operative to contract said one main die and to retain it'in contracted condition during opening of the wing die, and to expand the one main die after closure of the main dies and priorto closing of thewing dies'.

4. In a metal forming machine, a frame, a female die mounted thereon, a carriage mounted on the frame for movement toward and away from the female die, a I cooperable -male' die mounted on the carriage and having sections movable relatively toward and away from each other for expanding and contracting the male die, mechanical expandingmeans carried by the male die, retracting means carried by the male die, fluid pressure operated means carried by the carriage and connected to the mechanical expanding means and operative to move the mechanical expanding means for expanding the male die, and control means for the fluid pres sure operated means-operable independently of the position of the male die relative" to the female die.

5. An expansible die for a tangent bending machine of the character de'scribed'comprising a reciprocable die having a fixed die section and a movable die section mounted-on the flxedsection for movement relative thereto from contracted position to expanded-position, means yieldably urging said movable section'to, "and normally yieldably holding it in, contracted position, expanding means operatively interposed between the sections and movable in one direction to move the movable section to expanded position and in the opposite directionto'release the movable section for return to'contracted' position, an operating rod' extending "vertically through the sections and movable-axially relative thereto, meansoperatively connecting the rod and saidexpanding means for operation of the expanding means consequent upon axial movement of the rod, a piston and cylinder assemblage mounted in fixed position relative to the fixed die section, means operatively connecting the piston of said assemblage and said'rod for reciprocating the rod by the'assemblage, and means to admit fluid-pressure to said assemblage for actuating the same to" move the piston in'a direction to expand the die.

' CYRIL'JyBATH.

REFERENCES CITED The following referenes are ofre'co'rdin the flle of this patent: I

UNITED STATES PATENTS 7 Date Number Name 2,275,174 Clements Mar. v3, 1942 2,287,933 Green 'June 30, 1942 2,476,595 

